1. Field of the Invention
The present invention relates to industrial food processing machines which are used for blanching food products with steam, and the means by which a seal is maintained to prevent the steam within the blancher from escaping. More specifically, the present invention relates to food blanchers in which water is utilized to maintain water seals which keep the steam from leaking from the blancher.
2. Description of the Prior Art
In the process of blanching food products such as particulate vegetables, one of the major expenses is the energy cost involved in generating the steam which is used within the blancher to heat the vegetables. This is a particularly significant problem because the food product somehow has to be moved from the exterior of the blancher into the blancher steam chamber to be steamed, and then moved again to the exterior of the blancher for further processing. Several different types of methods have been utilized to minimize the amount of steam which escapes from the blancher, thereby reducing the energy cost involved in steam production. In U.S. Pat. No. 4,092,911 to Goodale, valves having rotating paddles with peripheral sealing members on the paddles are utilized to drop particulate food product into and out of the steam chamber while the motor-driven paddles and peripheral sealing members maintain a seal between the steam chamber and the exterior of the blancher. A multiple tank blancher with a steam chamber formed by a hood having a lower margin which is submerged in two water tanks and troughs therebetween is disclosed in U.S. Pat. No. 3,880,068 to Goodale. The blancher also includes multiple conveyor apparatuses to move the food product through the tanks and steam chamber.
Blanchers with partially water-filled troughs which are positioned so that the lower margin of the entire cover rests within the troughs to form a water seal also have been utilized. In this type of blancher, the water seal prevents the escape of steam between the cover and the tank or base. Accordingly, while water-filled troughs do an acceptable job of maintaining a water seal around the periphery of the tank, efficient movement of food products from the ambient atmosphere into the steam atmosphere within the blancher chamber and out again, in a simple, efficient manner with a minimum of moving mechanical parts and without significant loss of steam, remains a problem. Steam blanchers typically have had a large number of moving mechanical parts which are utilized in moving the food product into and out from the steam chamber through sealed or partially sealed areas. These multiple moving parts, which must operate in both air and water environments are subject to fouling and corrosion, wear and breakdown.